Fast Measurement of Droplet Parameters in Industrial Printing System

ABSTRACT

A droplet measurement system (DMS) is used in concern with an industrial printer used to fabricate a thin film layer of a flat panel electronic device. A clear tape serves as a printing substrate to receive droplets from hundreds of nozzles simultaneously, while an optics system photographs the deposited droplets through the tape (i.e., through a side opposite the printhead). This permits immediate image analysis of deposited droplets, for parameters such as per-nozzle volume, landing position and other characteristics, without having to substantially reposition the DMS or printhead. The tape can then be advanced and used for a new measurement. By providing such a high degree of concurrency, the described system permits rapid measurement and update of droplet parameters for printers that use hundreds or thousands of nozzles, to provide a real-time understanding of per-nozzle expected droplet parameters, in a manner that can be factored into print planning.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. Utility patent applicationSer. No. 14/840,343, for “Fast Measurement Of Droplet Parameters InIndustrial Printing System,” filed on behalf of first named inventorChristopher R. Hauf on Aug. 31, 2015 (the '343 application). The '343application claims priority to U.S. Provisional Patent Application No.62/044,958, for “Fast Measurement Of Droplet Parameters In IndustrialPrinting System,” filed on behalf of first named inventor Christopher R.Hauf on Sep. 2, 2014. The '343 application is also claims priority to,and is a continuation in-part of U.S. patent application Ser. No.14/340,403 for “Techniques for Print Ink Droplet Measurement and Controlto Deposit Fluids within Precise Tolerances,” filed on behalf of firstnamed inventor Nahid Harjee on Jul. 24, 2014. U.S. patent applicationSer. No. 14/340,403 in turn claims priority to U.S. Provisional PatentApplication No. 61/950,820 for “Techniques For Print Ink Droplet VolumeMeasurement And Control Over Deposited Fluids Within PreciseTolerances,” filed on behalf of first named inventor Nahid Harjee onMar. 10, 2014. U.S. patent application Ser. No. 14/340,403 in turnclaims priority to, and is itself a continuation in-part of each of PCTPatent Application No. PCT/US2014/035193 for “Techniques for Print InkDroplet Measurement and Control to Deposit Fluids within PreciseTolerances,” filed on behalf of first named inventor Nahid Harjee onApr. 23, 2014 and U.S. Utility patent application Ser. No. 14/162,525for “Techniques for Print Ink Volume Control To Deposit Fluids WithinPrecise Tolerances,” filed on behalf of first named inventor NahidHarjee on Jan. 23, 2014. U.S. Utility patent application Ser. No.14/162,525 in turn claims priority to Taiwan Patent Application No.102148330, filed for “Techniques for Print Ink Volume Control To DepositFluids Within Precise Tolerances” on behalf of first named inventorNahid Harjee on Dec. 26, 2013, and PCT Patent Application No.PCT/US2013/077720, filed for “Techniques for Print Ink Volume Control ToDeposit Fluids Within Precise Tolerances” on behalf of first namedinventor Nahid Harjee on Dec. 24, 2013. PCT Patent Application No.PCT/US2013/077720 claims priority to each of: U.S. Provisional PatentApplication No. 61/746,545, for “Smart Mixing,” filed on behalf of firstnamed inventor Conor Francis Madigan on Dec. 27, 2012; U.S. ProvisionalPatent Application No. 61/822,855 for “Systems and Methods ProvidingUniform Printing of OLED Panels,” filed on behalf of first namedinventor Nahid Harjee on May 13, 2013; U.S. Provisional PatentApplication No. 61/842,351 for “Systems and Methods Providing UniformPrinting of OLED Panels,” filed on behalf of first named inventor NahidHarjee on Jul. 2, 2013; U.S. Provisional Patent Application No.61/857,298 for “Systems and Methods Providing Uniform Printing of OLEDPanels,” filed on behalf of first named inventor Nahid Harjee on Jul.23, 2013; U.S. Provisional Patent Application No. 61/898,769 for“Systems and Methods Providing Uniform Printing of OLED Panels,” filedon behalf of first named inventor Nahid Harjee on Nov. 1, 2013; and U.S.Provisional Patent Application No. 61/920,715 for “Techniques for PrintInk Volume Control To Deposit Fluids Within Precise Tolerances,” filedon behalf of first named inventor Nahid Harjee on Dec. 24, 2013. PCTPatent Application No. PCT/US2014/035193 further claims the benefit ofU.S. Provisional Patent Application No. 61/816,696 for “OLED PrintingSystems and Methods Using Laser Light Scattering for Measuring Ink DropSize, Velocity and Trajectory” filed on behalf of first named inventorAlexander Sou-Kang Ko on Apr. 26, 2013, and of U.S. Provisional PatentApplication No. 61/866,031 for “OLED Printing Systems and Methods UsingLaser Light Scattering for Measuring Ink Drop Size, Velocity andTrajectory” filed on behalf of first named inventor Alexander Sou-KangKo on Aug. 14, 2013. Priority is claimed to each of the aforementionedapplications and each of the aforementioned patent applications ishereby incorporated by reference.

BACKGROUND

Industrial fabrication processes are increasingly turning to printingsystems to fabricate layers of products. These printing systems deposita fluid, which is then cured or hardened to form a permanent layer of aparticular product. These fabrication processes are especially usefulfor the fabrication of microelectronic products or products with arraysof quasi-electronic structures. For example, such printing processes areincreasingly being used to manufacture thin film electronic displays andsolar panels for a wide variety of applications. The mentioned printingsystems are typically characterized by, in addition to the type of fluidutilized (“ink”), the use of many thousands of print nozzles on one ormore printheads that are designed with capabilities to place individual,substantially uniform size droplets with near micron resolution. Thisprecision control over both deposited droplet volume and position helpsfacilitate high quality in end-products as well as high-resolution,small footprint products and reduced manufacturing costs. For example,in one application, namely the manufacture of organic light emittingdiode (OLED) displays, the ability to precision deposit the inks helpsproduce smaller, thinner, more resolute displays at lower cost. Notethat while the term “ink” is used to refer to the deposited fluid, thedeposited fluid is typically colorless, and is deposited as a structurethat will “build” a thickness of a permanent layer of a device, i.e.,the color of the fluid itself is typically not important in the sense itwould be for ink used in a conventional graphics printing application.

Not surprisingly, in these applications, quality control is dependent onuniformity in deposited ink droplets, as to size (droplet volume) andprecise position, or at least an understanding as to variation in suchfeatures is important to be able to produce permanent layers thatconsistently meet desired quality standards for layer registrationaccuracy and/or layer homogeneity. Note that in an industrial printingsystem, droplet uniformity for any given nozzle can also potentiallychange over time, whether due to statistical variation, changes innozzle age, clogging, ink viscosity or constituency variation,temperature, or other factors.

What is needed is a droplet measurement system adapted for use inconnection with an industrial printing process, ideally, for in situ usewith a printing system used by an industrial fabrication apparatus.Ideally, such a droplet measurement system would provide near fastmeasurement of one or more droplet parameters, be easy to maintain, andprovide inputs that could be used to adjust printing, so as to enableprecise quality control for used in the industrial product fabricationprocesses. The present invention addresses these needs and providesfurther, related advantages.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow chart illustrating techniques for measuring a dropletparameter.

FIG. 2 is a close-up perspective view of a droplet measurement system.

FIG. 3 is a cross-sectional view of a droplet measurement system.

FIG. 4A is another perspective view of a droplet measurement system.

FIG. 4B is a perspective view of the droplet measurement system fromFIG. 4A taken from the vantage point of arrow B-B in FIG. 4A.

FIG. 5A is a flow chart associated with image processing techniques usedin one embodiment.

FIG. 5B is a sample captured image representing drops deposited on amedium, following conversion to grayscale.

FIG. 5C is the captured image of FIG. 5B following filtering (e.g.,gradient processing).

FIG. 6A is an illustrative diagram showing manufacturing tiersassociated with product fabrication; the techniques disclosed herein canbe implemented, without limitation, in any of the depicted tiers.

FIG. 6B shows a fabrication apparatus in plan view.

FIG. 7A is an illustrative representation regarding use of a dropletmeasurement system.

FIG. 7B is a flow chart relating to droplet measurement.

FIG. 7C is a flow chart relating to droplet validation.

FIG. 8A is a cross-sectional representation of elements of an industrialprinter, internal to a print chamber.

FIG. 8B is a cross-sectional representation of the industrial printer ofFIG. 7A, taken along lines B-B in FIG. 8A.

FIG. 9 is a diagram showing a comparison of measured droplet positionsrelative to respective expected positions.

FIG. 10 is a flow chart relating to droplet volume computation.

The subject matter defined by the enumerated claims may be betterunderstood by referring to the following detailed description, whichshould be read in conjunction with the accompanying drawings. Thisdescription of one or more particular embodiments, set out below toenable one to build and use various implementations of the technologyset forth by the claims, is not intended to limit the enumerated claims,but to exemplify their application. Without limiting the foregoing, thisdisclosure provides several different examples of a droplet measurementsystem that optically measures or images deposited droplets on a medium,and that uses image processing to identify values of a parameter forvarious nozzles of a printhead used in industrial fabrication. Thevarious techniques can be embodied as a droplet measurement system, as aprinter or fabrication apparatus, or as software for performingdescribed techniques, in the form of a computer, printer or other devicerunning such software, or in the form of an electronic or other device(e.g., a flat panel device or other consumer end product) fabricated asa result of these techniques. While specific examples are presented, theprinciples described herein may also be applied to other methods,devices and systems as well.

DETAILED DESCRIPTION

In one embodiment, a droplet measurement system receives ink dropletsfrom various nozzles of one or more printheads, and then uses opticalanalysis to measure a value of a parameter associated with the variousdroplets and/or the various printhead nozzles that produced thosedroplets. More specifically, as will be discussed below, someembodiments use deposition tape in a printer maintenance bay for testprinting of the ink concurrently from various nozzles. The tape canadvantageously be any medium capable of receiving ink droplets, althoughin notable embodiment discussed below, it comprises a clear film that isspecially treated to fix wet ink droplets, much like photographic paper.Also in one embodiment, this system is applied in an industrialfabrication apparatus where droplets to be deposited are themselvesclear or translucent (for example, representing a material that will bedeposited and cured to form an encapsulation layer of a panel device,such as a display or solar panel, or light generating elements of such adevice). This transparency permits image capture of groupings of one ormore droplets for a set of multiple nozzles; in optional embodiments,the droplet depositions can be distinguished from both the film andimaged nozzle locations (behind the film) to provide extremely fastmeasurement of droplet positional offset (relative to ideal dropletposition) and/or volume and/or timing errors associated with dropletdeposition.

In one embodiment, to perform measurement, the printhead or printheadsare parked in a maintenance station, for example, while a substrate isloaded or unloaded into the printer (and thus, while theprinter/fabrication apparatus is otherwise employed). While theprintheads are parked, the droplet measurement system is engaged tobring the deposition medium (e.g., the clear film) into close proximitywith one or more printheads in a manner registered at a specificposition relative to the one or more printheads. Nozzles from one ormore of the printheads (e.g., a window or subarray comprising a subsetof all nozzles) are then cause to fire one droplet or a series ofdroplets (e.g., 2, 5, 10, etc.), such that the droplets land on themedium close to a position expected for the given nozzle. During thistime, or after this time, the film is imaged from a side of the filmopposite the printhead, effectively through the transparent film; thisis to say, the film is precisely positioned at a normal depositiondistance relative to the nozzles being measured (e.g., <1.0 millimeters)and measurement is simultaneously (or shortly later) performed onmultiple nozzles simultaneously by firing those nozzles, and then bycapturing an image through the opposite side of the film, with theresultant captured image then being image processed to derived dropletparameter values.

Note several advantages to features of the various embodiments describedso far. First, the mentioned optical processing of deposited dropletsthrough the clear film is especially useful for very large printheadshaving hundreds to many thousands of nozzles, i.e., optical processingcan be immediately performed without the requirement of further movingthe printhead, the droplet measurement system or other components.Second, the droplet measurement system can be configured to measuredroplets from many nozzles at the same time; for example, it is possibleto jet, and concurrently measure, droplets from hundreds of nozzles.When compared to systems that optically image individual droplets inflight for example, e.g., one at a time, this type of concurrency can domuch to facilitate measurement of droplets across many thousands ofprinthead nozzles (e.g., as is used in some industrial fabricationapplications). For systems that rely on dynamically updated measurementof droplet parameters, so as to combine droplets in a manner thatmitigates variation or that accounts for variation in producing precisetarget volumes, this type of concurrency can be important, because itdoes not require significant interruption in print time or inmanufacturing throughput. For a droplet measurement system thatarticulates relative to parked printhead or printheads in a servicestation, this provides for easy, precision access to any of thousands ofprint nozzles as can be used in some industrial manufacturing processes.Also, the deposition tape or its treatment can be specially adapted tothe chemical properties of a specific ink under test (i.e., to enableits properties to be more readily or more precisely ascertained byoptical means). As should be apparent, the described techniques providefor enhanced accuracy and lower cost in manufacturing products, e.g.,especially price-sensitive consumer products such as flat panel highdefinition televisions (“HDTVs”).

For at least one design discussed below, the droplet measurement systemmounts a clear film using a roll-to-roll mechanism, which permitsadvance of the film as a tape across an imaging area, permitting forintermittent change of tape rolls used for measurement. In addition, thedroplet measurement system can also advantageously use a vacuum systemwhich closely adheres that portion of the tape being deposited on in aflat, precise positional relationship that mimics an online depositionsurface. The droplet measurement system can also optionally include acure station to cure/dry ink, such that excess ink is inhibited fromspread to any other portion of the system following measurement; notethat this is not necessary in some embodiments, e.g., the film can alsobe selected to have properties or be treated to have properties suchthat the ink droplets once deposited are immediately fixed. Also, asnoted, the droplet measurement system can optionally be mounted on athree-dimensional movable mount, i.e., so as to engage a parkedprinthead from below along a vertical (“z”) axis and to move as desiredalong x (and optionally y) axes so as to reach different nozzles anddifferent printheads. This permits a “large” printhead assembly (e.g.,having thousands of nozzles) to be left stationary while the dropletmeasurement system is articulated beneath a printing plane (e.g., in amaintenance bay) and used to measure parameters for different groups ofnozzles. One contemplated deposition process advances a roll of tapesuch that a window of virgin tape is adjacent selected printheads, theseprintheads then are controlled to have all of their nozzles eject apredetermined amount of ink, which is then fixed on the tape;simultaneously, a coaxial camera and image sensor from below (e.g.,within a housing or chassis of the droplet measurement system) imagesall deposited droplets in parallel (once again, by image capture throughan opposite site of the tape, such that the film and droplet measurementsystem typically does not have to be moved or repositioned foranalysis). If desired, the camera (or image capture optics) can be mademovable relative to the droplet measurement system, e.g., to provide forscanning activity across a range of nozzles, focus adjustment, or otherdesired benefit.

The output of an image processing system then provides droplet parameterdata that is useful in validating nozzles or otherwise planningprinting. Following any given measurement iteration, the tape and thedroplet measurement system are each advanced in position, with used tapebeing cured and/or rolled up, and the process is then repeated asnecessary, immediately or at a later time. In a design where the tapecannot be reused once printed upon, a spent roll of tape (or a tapecartridge, with reels for new and used tape and capstans) can beperiodically collected or replaced on a modular basis. Note that in onecontemplated application, in which a fabrication mechanism iscontinuously used (e.g., to print layers of OLED television screens, orotherwise to fabricate a layer of one or more flat panel devices), as aprior substrate is or unloaded, the printhead is parked and subjected todescribed droplet measurement, and as soon as a new, ensuing substrateis ready, the measurement progress is stored, the printhead returned toactive printing duty, and so forth; when this ensuing substrate isfinished, the printhead is once again returned to the maintenancestation (while a new substrate is loaded) to begin measurement where thesystem previously left off. In this manner, repeated measurements can becollected for nozzles and used on a rolling basis to build a statisticaldistribution for each print nozzle or nozzle-waveform combinationthrough many measurements (e.g., as described in the aforementionedpatent applications which have been incorporated by reference), using amoving measurement window that precesses circularly through the set ofall print nozzles so as to continuously update measurement data.

Note that all of the process steps recited above (as well as below) canbe implemented in a number of manners. For example, in one embodiment,these steps are performed by one or more computers or other types ofmachines (such as a printer or one or more manufacturing devices),either by special purpose hardware or by general purpose hardware thatis configured to operate as a special purpose machine. For example, inone contemplated design, one or more of the tasks can be performed byone or more such machines acting under the control of instructionsstored on non-transitory machine-readable media, e.g., firmware orsoftware. Such instructions are written or designed in a manner that hascertain structure (architectural features) such that, when they areultimately executed, they cause the one or more general purpose machines(e.g., a processor, computer or other machine) to behave as a specialpurpose machine, having structure that necessarily performs describedtasks on input operands to take actions or otherwise produce outputs.“Non-transitory machine-readable media” means any tangible (i.e.,physical) storage medium, irrespective of how data on that medium isstored, including without limitation, random access memory, hard diskmemory, optical memory, a floppy disk or CD, server storage, volatilememory and other tangible mechanisms where instructions may subsequentlybe retrieved by a machine. The machine-readable media can be instandalone form (e.g., a program disk) or embodied as part of a largermechanism, for example, a laptop computer, portable device, server,network, printer, or other set of one or more devices. The instructionscan be implemented in different formats, for example, as metadata thatwhen called is effective to invoke a certain action, as Java code orscripting, as code written in a specific programming language (e.g., asC++ code), as a processor-specific instruction set, or in some otherform; the instructions can also be executed by the same processor ordifferent processors, depending on embodiment. Throughout thisdisclosure, various processes will be described, any of which cangenerally be implemented as instructions stored on non-transitorymachine-readable media, and any of which can be used to fabricateproducts using a “3D printing” or other printing process. Depending onproduct design, such products can be fabricated to be in saleable form,or as a preparatory step for other printing, curing, manufacturing orother processing steps, that will ultimately create finished productsfor sale, distribution, exportation or importation. Depending onimplementation, the instructions on non-transitory machine-readablemedia can be executed by a single computer and, in other cases, can bestored and/or executed on a distributed basis, e.g., using one or moreservers, web clients, or application-specific devices. Each functionmentioned can be implemented as part of a combined program or as astandalone module, either stored together on a single media expression(e.g., single floppy disk) or on multiple, separate storage devices.

Note also that “clear” when used in connection with the film or tape isa relative term, i.e., it refers to the ability to capture an image ofdroplets deposited on a first side of the tape through a second side ofthe tape. This does not, strictly speaking, require the tape to becolorless or for that matter, transparent to visible light. In oneembodiment, the tape is colorless and highly transparent to visiblelight, and visible light is used to capture an image of droplets fromrespective nozzles, where those droplets are deposited in a manner suchthat respective nozzles' droplets are arrayed on the first side of thetape (i.e., at respective positions correlated with the respectivenozzles). In another embodiment, the tape has some degree of color, forexample, optimized to a specific ink so as to enhance image captureproperties of that ink. In yet another embodiment, radiation other thanvisible light is used to capture droplet properties.

Various other features will be apparent to those skilled in the art fromthe description herein. Having thus introduced features of severalembodiments, this disclosure will now turn to providing additionaldetail regarding select embodiments.

FIG. 1 shows a flow diagram 101 that illustrates some of the techniquesdescribed herein. As indicated above, it is desired to concurrentlymeasure values of droplet parameters for droplets produced by amultitude of nozzles. In order to perform this as rapidly as possible,embodiments disclosed herein rely on image capture of a depositionsurface that receives such droplets (i.e., fast capture of dropletscollectively representing the multiple nozzles), and image processingthat computes values of one or more desired parameters respective to themultiple nozzles from this image capture. As noted by reference numeral103, the printhead or printheads under analysis cause a range or arrayof nozzles to fire, to each thereby deposit one or more droplets. Toprovide an example, it could be that a hypothetical printhead has twothousand nozzles, and that these nozzles are to be measured in groups ofone hundred nozzles at a time. For each measurement iteration, theprinthead and/or the droplet measurement system are aligned, and thewindow or group of one hundred nozzles to be measured are identified andcaused to fire a controlled ink volume substantially concurrently; inone embodiment, the deposition can be a single droplet per nozzle, andin other embodiments, a larger number of droplets can be controllablyejected from each nozzle, for example, 2, 5, 10, 12, 20 or some othernumber of droplets. Note that in some contemplated designs (e.g., OLEDapplications), droplet size is typically quite small, comprisingpicoliter (“pL”) size droplets that are tens of microns in diameter orsmaller, deposited with near-micron precision.

As noted in the aforementioned patent applications incorporated byreference, depending on application, it may be desired to measureposition of deposited droplets, droplet velocity, droplet volume, nozzlebow, or one or more other parameters for each nozzle. Briefly, in oneembodiment, it is important to have an expectation of droplet qualitiesfrom each nozzle for each deposited droplet; this is to say, if onenozzle relative to others is off position (nozzle bow) or producesaberrant droplet trajectory or an inaccurate droplet volume, then thiscould lead to nonuniformity in a deposited film. Such nonuniformity canlead to quality defects in precision products, for example, displaydevices and the like. An understanding nozzle-by-nozzle of suchaberration permits:

-   -   (a) nozzle qualification/disqualification—a nozzle that does not        work or otherwise has aberrant characteristics can be identified        and not used in printing, with software planning printing in a        manner where a different nozzle is used to deposit a droplet in        the desired area;    -   (b) firing time mitigation—a positional defect in the scanning        direction can be potentially corrected by changing a nozzle        drive pulse as to timing or voltage, for example, such that the        nozzle fires earlier or later, or ejects droplets with a greater        or lesser velocity; in addition, it is also possible to use        alternate drive pulse shapes as disclosed in the aforementioned        patent applications which have been incorporated by reference;    -   (c) planned droplet combinations—detected differences from        nozzle-to-nozzle can be accepted and deliberately used in        calculating droplet combinations based on respective, expected        values, to achieve a precise result, e.g., within a specific        tolerance; for example, if one nozzle is measured and determined        to produce expected 9.89 picoliter (pL) droplets, a second        nozzle is measured and determined to produce expected 10.11 pL        droplets and it is desired to produce a total volume of 20.00 pL        ink in a specific target location, these two nozzles can be        specifically identified and printing planned to deposit this        specific droplet combination; note that obtainable results are        different from a system that simply averages out differences        without regard to a specific fill volume or fill tolerance        (e.g., a target volume ±0.50%); and    -   (d) prescreening of drive waveforms—as noted in the        aforementioned patent applications which have been incorporated        by reference, it is possible to prescreen programmable drive        waveforms for each nozzle (e.g., a choice of sixteen preselected        drive waveforms) for stock use during printing, each waveform        selected to achieve a specific deposition characteristic, with        precision, expected results.

Note that droplet parameters can potentially vary from day-to-day, andeven from deposition-to-deposition, e.g., dependent on ink qualities,temperature, nozzle age (e.g., clogging) and other factors. To ensureprecision printing therefore, in some implementations, it can be desiredto remeasure these values from time-to-time. Note also that eachdeposited droplet, even from a single nozzle, can be slightly different;in one embodiment therefore, each nozzle (or nozzle-waveform combinationor pairing) is measured not just once, but multiple times, to develop apopulation of measurements, from which a mean or other statisticalparameter (e.g., a spread measure) can be computed so as to provide ahigh confidence regarding expected values for droplet parameters. Forexample, “24” droplets from each nozzle-waveform pairing could bemeasured to develop means (and thus an expected value for) volume,velocity, bow (position orthogonal to scanning direction), and so forth,with the number of measurements n (n=24) helping reduce uncertainty dueto measurement error or statistical variation. A given population can beupdated on a rolling basis (e.g., all measurements stored and 6 newestmeasurements replacing 6 oldest for each nozzle every two hours), or onan at-once basis (e.g., all nozzles remeasured at once during power-up).There are many variations that will occur to those skilled in the art,e.g., a nozzle can be measured to determine an expected value and thenozzle disqualified from use if this measured (expected) value isoutside of a band that is ±5% of an ideal value; many permutations andvariations are clearly possible.

As should be apparent, however, in a printing system that uses thousandsof nozzles (e.g., tens of thousands of nozzles or more, perhaps eachwith multiple available “prescreened” drive waveforms), measurement ofexpected droplet parameters for each nozzle could potentially takesubstantial time; in an industrial fabrication environment, this istypically unacceptable, i.e., to be commercially viable, manufacturingthroughput and costs need to produce products at an acceptable consumerprice point, and this typically means that the print process produces asmany products as possible, with as great an accuracy (and as littleproduct waste) as possible, with as little down time as possible. Thetechniques disclosed herein permit much more rapid and, thus, feasiblemeasurement.

Returning to FIG. 1, to this effect, the droplet measurement techniquespresented by this disclosure also capture droplets from many nozzles atonce, per numeral 105. That is to say, as contrasted with systems thatimage droplets in flight “one-at-a-time,” embodiments presented by thisdisclosure rely on concurrency to measure as many nozzles as possible atthe same time. Thus, image capture can be used to effectively take apicture of droplets from a large array of nozzles, e.g., dropletsdeposited in multiple columns and in multiple rows, which are quicklyprocessed in software by an image processing system. In one embodiment,a captured image can represent droplets from dozens, and potentiallyhundreds of nozzles (or more), all measured at the same time. FIG. 1indicates in dashed-line boxes various options that can contribute tothis end, for example, (a) capturing images through the depositionsurface opposite the printhead (107), which helps speed measurement, (b)capturing droplets and nozzles both in a captured image at the same time(109), which facilitates measurement of positional offset, bow, orvelocity for droplets from respective nozzles, (c) photographingdroplets from respective (multiple) nozzles at the same time (111),e.g., effectively measuring forty or more nozzles at once, and (d)photographing not one droplet per nozzle, but an aggregation of multipledroplets, e.g., 5 or more, measured at the same time. Note that in thelatter case, image processing software can detect volume of an aggregatedeposition (e.g., volume), or spread in terms of droplet position aroundan expected position, and can identify individual droplets, mean, oranother statistical parameter such as distribution (spread) at once froma single captured image. Note that this may require, depending onembodiment, that a standard be measured in advance and stored in thesystem; for example, as ink droplets are fixed into the depositionmedium (i.e., the tape), it may be difficult to detect droplet volume;such a determination can be predicated on droplet diameter, processingof color (or grayscale) value of a deposited droplet, or using othermeans, with these values compared to a calibration standard in order toproduce accurate value computation.

As noted by numerals 115 and 117, the system (e.g., using an imageprocessor running appropriate software) then calculates measured valuesand stores these in memory (e.g., random access memory such as in anavailable hard disk drive). In one embodiment, these values are storedindividually (i.e., one for each measurement for each parameter beingmeasured for each nozzle) and in another embodiment, they can be storedin a manner representing a composite distribution (e.g., as a mean,total number of measurements, standard deviation, etc., for a givenparameter for a given nozzle). Per numerals 119, 121 and 123, as notedearlier, the values once measured can be optionally used to compute astatistical distribution, to perform nozzle qualification/validation,and to perform “smart combinations” where print scans are planned tomatch droplets with expected characteristics in some desired manner.

FIGS. 2-4B are used to describe one embodiment of a modular dropletmeasurement system.

FIG. 2 shows a close up view of a first such system 201. This viewdepicts a measurement window 203 (e.g., a glass-covered view window)through which images are captured along a vector represented by numeral205. An optical detector, for example a camera, lies within system 201and takes pictures through this window 203 along the direction of arrow205. During operation, a clear film tape from roll 207 is advanced overthis window and is held tight against the window by a set of vacuumports 209. Following each measurement, this tape can be advanced in thedirection of capstan 211 and accumulated in a discard roll (not seen)held within a chassis 213 of the droplet measurement system. Note thatthe depicted system is modular and is moved as a unit, e.g., to positionthe measurement window 203 (and associated measurement area defined bythis window) in close proximity to any printhead nozzles to be measured,at a “standard deposition depth” relative to a nozzle plate of theprintheads. In optional embodiments, the droplet measurement system 201can be articulated in three dimensions so that this system can be placedadjacent other nozzle sets and also so as to vary deposition height asdesired.

FIG. 3 shows an interior, cross-sectional view of the dropletmeasurement system 301. This system similarly includes a view window 303through which images are captured and an optics system comprising anoptics assembly 305, a camera 307 and a light source 309. A steppermotor 311 selectively advances the optics assembly 305 linearly relativeto the view window 303, i.e., back and forth in the direction indicatedby arrows 313. Note that “camera” as used herein can optionally refer toany type of light sensor, i.e., it is possible to use a simple linesensor comprising individual optical sensors and for example to “scan”such a line sensor back and forth to image the entire viewing window 303using this stepper motor 311. In other embodiment embodiments, thecamera captures an image representing an array of pixels of the viewarea through any conventional means, e.g., using a commercialphotographic camera, charge couple device array, an ultraviolet or othernonvisible radiation capture device, or with other means. Note thatcamera movement (i.e., scanning movement) is not required for allembodiments. In the depicted embodiment, the optics assembly 305 alsointernally comprises a beam splitter which passes light from the lightsource (e.g., up to the view window 303), but diverts returning(reflected) light using a mirror in the direction of the camera 307, forimage capture. As should be apparent, light form the light source passesthrough the view window, through the clear tape, reflects against theprinthead (not shown in FIG. 3), passes back again through the cleartape, and subject to any focusing or other optics, is captured andprocessed for analysis. A captured image thus provides visibleindication of the position of each nozzle being measured (e.g., thisimage is captured from reflection by the nozzle plate) and also showsoverlay of any deposited droplets (which are transparent, butdistinguishable from the film). This is to say, in contemplatedmanufacturing processes (particularly for OLED display fabrication,e.g., for an encapsulation layer), deposition materials are translucent,and thus do not occlude image capture of the nozzle plate. FIG. 3 alsoshows a capstan 315 for transport of the clear tape and a UV curing bar317 for curing any deposited ink, so as to prevent transfer of depositedink to any other system component. FIG. 3 also shows an interface andcontrol board 319, used for control over the various system components,and for control over image capture; the interface control board 319 alsocontrols transport of the film tape, for example, by controlling filmroll motors 321 and 323 respectively used for film intake and supplyrolls (not separately identified this FIG.). Image processing can be,depending on embodiment, performed either locally on the interface andcontrol board 319 or alternatively, at a processor in the manufacturingapparatus or at a remote computer.

FIGS. 4A and 4B show perspective views of the droplet measurement system301 from FIG. 3. FIG. 4B represents a view of the backside of the unitrelative to FIG. 4A, that is, from the vantage point provided by arrowB-B of FIG. 4A. More specifically, these FIGS. identify view window 303,vacuum ports 403, UV curing bar 317, a tape supply roll 405 and intakeroll 407, a frame and optic chamber 409 (which houses the interface andcontrol board 319, as described earlier). During operation, virgin tapeis supplied in the direction indicated by arrow 411 and is adheredclosely against the view window 303, as referenced earlier. From thispoint, the film is advanced over capstan 315 and downward toward the UVcuring bar 317 along arrow 412, for the purposes described earlier.Operation of the UV curing bar is controlled by the interface andcontrol board 319, using onboard firmware or software stored onnon-transitory-machine readable media. Finally, following cure, film isadvanced generally as indicated by arrow 415 to the intake roll 407. Asshould be apparent, the entire unit is modular, providing for easyremoval and servicing, for example, to remove a finished intake roll 407of clear deposition tape and to change the supply roll 405 to have freshstock.

FIG. 5A presents a flow chart associated with one embodiment 501 of amethod of performing droplet measurement. As noted earlier, it can bedesired to perform measurement in situ, that is, directly within afabrication apparatus to dynamically update values of one or moredroplet parameters for process, age, temperature, or other factors. Tothis end, measurement is advantageously performed in a service stationof a printer, for example, while a new substrate is being loaded,unloaded, cured following deposition, or otherwise during idle timerelative to actual printing. Per numeral 503, one or more printheads(for example, mounted to a common printhead assembly) are advanced tothe service station and are “parked” for maintenance operations. Suchmaintenance operations can include various calibrations, printheadreplacement, nozzle purging or other quality processing, dropletmeasurement as contemplated by this disclosure, or for other purposes.As will be described more fully below, for OLED display fabricationapplications (and for fabrication of certain other devices, such assolar panels), it can be desired to perform printing in a controlledatmosphere; therefore, in many applications, the “parked” position willbe in a second controlled atmospheric chamber, for example, in alocation that can be externally accessed (e.g., for printheadreplacement) without venting the entire fabrication apparatus or printerto an uncontrolled atmosphere. This is to say, such a second chamber ispreferably made to be a small size relative to any printing enclosure,e.g., taking up two percent or less of the overall print chamber volume,so as to minimize venting (if any). Once the printheads are parked, theyare sealed against this second controlled atmosphere and the dropletmeasurement system (“DMU,” for droplet measurement unit) is selectivelyengaged to perform measurement (505). As noted by optional process block507, if printing is performed on an intermittent basis for a movingwindow of nozzles (e.g., with different sets of nozzles measured orremeasured in between print runs, as substrates are loaded and unloadedas mentioned earlier), the system retrieves a start address so as toposition the DMU to capture the selected subset of nozzles. Note thatthis process can employ a registration process to identify cornernozzles of each printhead (e.g., updated as a printhead is changed, suchthat the system is calibrated to “know” the approximate position of eachnozzle). Such a registration process can be performed by articulatingthe DMU (and its camera) so as to image and thereby find the cornernozzles for each array, using an approximate positional address andsearch process (e.g., spiral search algorithm), for example, asdescribed in U.S. patent application Ser. No. 14/340,403, referencedearlier. Control over positional throws is quite precise in thedescribed system, e.g., to approximately one micron, and typicallyrecalibration of printhead-to-droplet measurement system positioning isnot required unless a system component is manually changed (for example,the DMU or a printhead is removed or serviced). With a clear tape (i.e.,droplet deposition surface for testing) in place, per numeral 509, thesystem controls the printhead nozzles under scrutiny to each deposit acontrolled number of droplets (in quick succession if multiple dropletsare to be measured per-nozzle). Simultaneously, the image capture systemwithin the DMU images deposited ink as well as nozzle locations (e.g.,through the clear tape and the ink, capturing light reflected by theprinthead). Note that as indicated by numeral 511, in one embodiment,image capture is performed in color so as to be able to identifyconcentration of ink in any deposited ink droplets (e.g., which, whiletranslucent, will impart subtle color properties according to materialor thickness). As also indicated by numeral 511, a captured image can befiltered (e.g., for color, intensity, gamma, or any other desiredparameter or parameters) so as to yield a filtered image; following suchfiltering (or as part of such filtering), the captured image isconverted to grayscale, per numeral 513. Note that multiple images canalso be produced from this process according to respective filters, forexample, a first image representing the nozzles and a second imagerepresenting deposited droplets; clearly, many permutations exist. Imageprocessing software then uses the output grayscale image(s) to identifynozzles, ink droplets, positional differences between nozzles and inkdroplets, droplet volume, droplet diameter, droplet shape, and/or anyother desired parameters (515/517). As should be apparent, it is notnecessary to all embodiments that all of these things be measured. Forexample, in a system which calculates droplet volume, it may not benecessary to image nozzles themselves, or to analyze droplet shape orposition. Conversely, it may be important in such an embodiment (ifspread of multiple droplets is being analyzed) to determine a measure ofdeviation in droplet position, or to perform color analysis to properlycompute volume. The parameters that are measured will generally dependon implementation and desired results. As indicated by numeral 517,whatever the parameter to be measured, the system computes a measuredvalue or values, or an offset for a parameter, for example using anoptional standard 519, as referenced earlier. Such offset or value of aparameter can be computed for droplet or nozzle position, droplettiming, or droplet volume, or any combination of these things, asreferenced by numeral 521. The system then updates a stored informationrepository that is local or remote to the DMU (523) and it then storesposition for the next measurement iteration and advances the tape, peroptional process 525. The process is then done, ready for anothermeasurement iteration (which can be performed immediately, or at a latertime, e.g., following an ensuing substrate run).

Note that as referenced by numerals 529-533, computation of theparameter and/or any positional offset can be optionally performed byone or more processors running suitable software (instructions stored onprocessor-readable media), and that such processors typically storeimage data in processor-accessible memory, isolate image data respectiveto each nozzle, calculate the parameter from the respective image data,and also store the per-nozzle parameter in processor-accessible memory.

FIGS. 5B and 5C respectively show sampled images 551 and 571. The firstof these, image 551, represents a photograph taken of approximately 40nozzles as a subset of a printhead. Note how the nozzles are slightlystaggered from row-to-row to provide options for close pitch variationin a cross scan axis (e.g., a droplet intended for a specific substrateposition can be printed from any row of nozzles, providing depositionalaccuracy better than, i.e., less than, twenty microns in someembodiments). FIG. 5B represents a color image, which can then befiltered and/or converted to grayscale as appropriate, as well as agrayscale image following such filtering or conversion (i.e., colordrawings are generally not used or permitted in patent applications).Note that in this embodiment, the nozzles are not separately imaged orillustrated, although for other embodiments, they can be. The secondimage 571 (FIG. 5C) represents the image from FIG. 5B, followingfiltering and gradient processing, to identify droplet diameters. Thatis to say, FIG. 5C shows white circles corresponding to dropletdiameter, with clearly demarked droplet boundaries. Image processingcalculates a center of gravity (for example, by calculating a horizontalmaximum diameter and vertical maximum diameter of such “circles” and bytaking the medial Cartesian coordinate point along each diameter, toassociate each droplet with a specific xy Cartesian position). Thisposition can then be compared to nozzle position to determine offset,with the system identifying nozzle-to-nozzle offset variation, forpurposes of print planning. These photographs can also represent dropletvolume processing; for example, image processing software can computediameter and/or area of each droplet and/or associated color, andcompare this to a factory-defined standard or an in situ-definedstandard, to compute size and density and, from these, to computevolume. Nearly any desired droplet parameter can be measured in thisway.

With the particulars of a droplet measurement system thus described,application to manufacture and to an industrial fabricationapparatus/printer will now be described. In the discussion below, anexemplary system for performing such printing will be described, morespecifically, applied to the manufacture of solar panels and/or displaydevices that can be used in electronics (e.g., as smart phone, smartwatch, tablet, computer, television, monitor, or other forms ofdisplays). The manufacturing techniques provided by this disclosure arenot limited to this specific and, for example, can be applied to any 3Dprinting application and to a wide range of other forms of products.

FIG. 6A represents a number of different implementation tiers,collectively designated by reference numeral 601; each one of thesetiers represents a possible discrete implementation of the techniquesintroduced herein. First, techniques as introduced in this disclosurecan take the form of instructions stored on non-transitorymachine-readable media, as represented by graphic 603 (e.g., executableinstructions or software for controlling a computer or a printer). Forexample, the disclosed techniques can be embodied as software adapted tocause a manufacturing apparatus (or included printer) to measure one ormore droplet parameters using optical measurement techniques disclosedherein. Second, per computer icon 605, these techniques can alsooptionally be implemented as part of a computer or network, for example,within a company that designs or manufactures components for sale or usein other products. Third, as exemplified using a storage media graphic607, the techniques introduced earlier can take the form of a storedprinter control instructions, e.g., that, when acted upon, will cause aprinter to fabricate one or more layers of a component in a mannerdependent on droplet measurement and associated planning (e.g., scanpath planning or nozzle qualification, as discussed herein). Note thatprinter instructions can be directly transmitted to a printer, forexample, over a LAN or WAN; in this context, the depicted storage mediagraphic can represent (without limitation) RAM inside or accessible to aserver, portable device, laptop, another form of computer or a printer,or a portable media such as a flash drive. Fourth, as represented by afabrication device icon 609, the techniques introduced above can beimplemented as part of a fabrication apparatus or machine, or in theform of a printer within such an apparatus or machine (e.g., as adroplet measurement system according to techniques disclosed herein, asa method of manufacture, as software for controlling a dropletmeasurement system, and so forth). It is noted that the particulardepiction of the fabrication device 609 represents one exemplary printerdevice that will be discussed in connection with FIGS. 6B, 7A and 7B,below. The techniques introduced above can also be embodied as acompleted or partially-completed manufactured component or an assemblyof manufactured components (e.g. manufactured pursuant to a patentedprocess); in FIG. 6A for example, several such components are depictedin the form of an array 611 of semi-finished flat panel devices, thatwill be separated and sold for incorporation into end consumer products.The depicted devices may have, for example, one or more encapsulationlayers or other layers fabricated in dependence on the methodsintroduced above. The techniques introduced above can also be embodiedin the form of end-consumer products as referenced, e.g., in the form ofdisplay screens for portable digital devices 613 (e.g., such aselectronic pads or smart phones), as television display screens 615(e.g., OLED TVs), solar panels 617, or other types of devices.

FIG. 6B shows one contemplated multi-chambered fabrication apparatus 621that can be used to apply techniques disclosed herein. Generallyspeaking, the depicted apparatus 621 includes several general modules orsubsystems including a transfer module 623, a printing module 625 and aprocessing module 627. Each module maintains a controlled environment,such that printing for example can be performed by the printing module625 in a first controlled atmosphere and other processing, for example,another deposition process such an inorganic encapsulation layerdeposition or a curing process (e.g., for printed materials), can beperformed in a second controlled atmosphere. The apparatus 621 uses oneor more mechanical handlers to move a substrate between modules withoutexposing the substrate to an uncontrolled atmosphere. Within any givenmodule, it is possible to use other substrate handling systems and/orspecific devices and control systems adapted to the processing to beperformed for that module.

Various embodiments of the transfer module 623 can include an inputloadlock 629 (i.e., a chamber that provides buffering between differentenvironments while maintaining a controlled atmosphere), a transferchamber 631 (also having a handler for transporting a substrate), and anatmospheric buffer chamber 633. Within the printing module 625, it ispossible to use other substrate handling mechanisms such as a flotationtable for stable support of a substrate during a printing process.Additionally, a xyz-motion system, such as a split axis or gantry motionsystem, can be used for precise positioning of at least one printheadrelative to the substrate, as well as providing a y-axis conveyancesystem for the transport of the substrate through the printing module625. It is also possible within the printing chamber to use multipleinks for printing, e.g., using respective printhead assemblies suchthat, for example, two different types of deposition processes can beperformed within the printing module in a controlled atmosphere. Theprinting module 625 can comprise a gas enclosure 635 housing an inkjetprinting system, with means for introducing an inert atmosphere (e.g.,nitrogen) and otherwise controlling the atmosphere for environmentalregulation (e.g., temperature and pressure), gas constituency andparticulate presence.

Various embodiments of a processing module 627 can include, for example,a transfer chamber 636; this transfer chamber also has a including ahandler for transporting a substrate. In addition, the processing modulecan also include an output loadlock 637, a nitrogen stack buffer 639,and a curing chamber 641. In some applications, the curing chamber canbe used to cure, bake or dry a monomer film into a uniform polymer film;for example, two specifically contemplated processes include a heatingprocess and a UV radiation cure process.

In one application, the apparatus 621 is adapted for bulk production ofliquid crystal display screens or OLED display screens, for example, thefabrication of an array of (e.g.) eight screens at once on a singlelarge substrate. These screens can be used for televisions and asdisplay screens for other forms of electronic devices. In a secondapplication, the apparatus can be used for bulk production of solarpanels in much the same manner.

The printing module 625 can advantageously be used in such applicationsto deposit organic encapsulation layers that help protect the sensitiveelements of OLED display devices. For example, the depicted apparatus621 can be loaded with a substrate and can be controlled to move thesubstrate back and forth between the various chambers in a manneruninterrupted by exposure to an uncontrolled atmosphere during theencapsulation process. The substrate can be loaded via the inputloadlock 629. A handler positioned in the transfer module 623 can movethe substrate from the input loadlock 629 to the printing module 625and, following completion of a printing process, can move the substrateto the processing module 627 for cure. By repeated deposition ofsubsequent layers, each of controlled thickness, aggregate encapsulationor other layer thickness can be built up to suit any desiredapplication. Note once again that the techniques described above are notlimited to encapsulation processes or to OLED fabrication, and also thatmany different types of tools can be used. For example, theconfiguration of the apparatus 621 can be varied to place the variousmodules 623, 625 and 627 in different juxtaposition; also, additional,fewer or different modules can also be used.

While FIG. 6B provides one example of a set of linked chambers orfabrication components, clearly many other possibilities exist. Thetechniques introduced above can be used with the device depicted in FIG.6B, or indeed, to control a fabrication process performed by any othertype of deposition equipment.

FIGS. 7A-7C are used to generally introduce techniques and structuresused for per-nozzle droplet measurement and validation.

More particularly, FIG. 7A provides an illustrative view depicting adroplet measurement system 701 and a relatively large printhead assembly703; the printhead assembly has multiple printheads (705A/705B) eachwith a multitude of individual nozzles (e.g., 707), withhundreds-to-thousands of nozzles present. An ink supply (not shown) isfluidically connected with each nozzle (e.g., nozzle 707), and apiezoelectric transducer (also not shown) is used to jet droplets of inkunder the control of a per-nozzle electric control signal. The nozzledesign maintains slightly negative pressure of ink at each nozzle (e.g.,nozzle 707) to avoid flooding of the nozzle plate, with the electricsignal for a given nozzle being used to activate the correspondingpiezoelectric transducer, pressurize ink for the given nozzle, andthereby expel droplets from the given nozzle. In one embodiment, thecontrol signal for each nozzle is normally at zero volts, with apositive pulse or signal level at a given voltage used for a specificnozzle to eject droplets (one per pulse) for that nozzle; in anotherembodiment, different, tailored pulses (or other, more complexwaveforms) can be used nozzle-to-nozzle. In connection with the exampleprovided by FIG. 7A, however, it should be assumed that it is desired tomeasure a droplet volume produced by a specific nozzle or specific setof nozzles (e.g., nozzle 707) where a droplet is ejected downward fromthe printhead (i.e., in the direction “h,” representing z-axis heightrelative to a three-dimensional coordinate system 708) toward a chassis709 that mounts a deposition film. As noted earlier, for embodimentswhich use current droplet deposition from many nozzles, a target surfaceis advantageously both fixed in a known position relative to theprinthead (e.g., such that it is known which deposited droplets belongto which nozzle). The dimension of “h” is typically on the order of onemillimeter or less and that there are thousands of nozzles (e.g., 10,000nozzles) that are to have respective droplets individually measured inthis manner within an operating printer, with the deposition surfacebeing changed or advanced in increments to multiple windows where manydroplets (e.g. dozens to hundreds) will be simultaneously imaged andmeasured. Thus, in order to optically measure droplets from each nozzlewith precision, certain techniques are used in disclosed embodiments toappropriately position elements of the droplet measurement system 701,the printhead assembly 703, or both relative to one another for opticalmeasurement.

In one embodiment, these techniques utilize a combination of (a) x-ymotion control (711A) of at least part of the optical system (e.g.,within dimensional plane 713) to precisely position a measurement area715 presented by the system immediately adjacent to any nozzle or set ofnozzles that is to produce droplets for optical calibration/measurementand (b) below plane optical recovery (7118) (e.g., thereby permittingeasy placement of the measurement area next to any nozzlenotwithstanding a large printhead surface area). Thus, in an exemplaryenvironment having about 10,000 or more print nozzles, this motionsystem is capable of positioning at least part of the optical system in(e.g.) 10,000 or so discrete positions proximate to the discharge pathof each respective nozzle of the printhead assembly. Optics aretypically adjusted in position so that precise focus is maintained onthe measurement area so as to capture deposited droplets on a clear filmor other deposition media, as mentioned. Note that a typical droplet maybe on the order of microns in diameter, so the optical placement istypically fairly precise, and presents challenges in terms of relativepositioning of the printhead assembly and measurement optics/measurementarea. In some embodiments, to assist with this positioning, optics(mirrors, prisms, and so forth) are used to orient a light capture pathfor sensing below the dimensional plane 713 originating from themeasurement area 715, such that measurement optics can be placed closeto the measurement area without interfering with relative positioning ofthe optics system and printhead. This permits effective positionalcontrol in a manner that is not restricted by the millimeter-orderdeposition height h at which each droplet is deposited and imaged or thelarge scale x and y width occupied by a printhead under scrutiny.Optionally, separate light beams incident from different angles can beused to image a film or deposition surface from underneath, or a coaxialimage capture system with a beam splitter can also be used. Otheroptical measurement techniques can also be used. In an optional aspectof these systems, the motion system 711A is optionally andadvantageously made to be an xyz-motion system, which permits selectiveengagement and disengagement of the droplet measurement system withoutmoving the printhead assembly during droplet measurement. Brieflyintroduced, it is contemplated in an industrial fabrication devicehaving one or more large printhead assemblies that, to maximizemanufacturing uptime, each printhead assembly will be “parked” in aservice station from time to time to perform one or more maintenancefunctions; given the sheer size of the printhead and number of nozzles,it can be desired to perform multiple maintenance functions at once ondifferent parts of the printhead. To this effect, in such an embodiment,it can be advantageous to move measurement/calibration devices aroundthe printhead, rather than vice-versa. [This then permits engagement ofother non-optical maintenance processes as well, e.g., relating to othernozzles if desired.] To facilitate these actions, the printhead assemblycan be optionally “parked,” as mentioned with the system identifying aspecific group or range of nozzles that are to be the subject of opticalcalibration. Once the printhead assembly or a given printhead isstationary, the motion system 711A is engaged to move at least part ofthe optics system relative to the “parked” printhead assembly, toprecisely position the measurement area 715 at a position suitable fordetecting droplets jetted from a group of respective nozzles; the use ofa z-axis of movement permits selective engagement of light recoveryoptics from well below the plane of the printhead, facilitating othermaintenance operations in lieu of or in addition to optical calibration.Perhaps otherwise stated, the use of an xyz-motion system permitsselective engagement of the droplet measurement system independent ofother tests or test devices used in a service station environment. Forexample, in such a system, one or more printheads of a printheadassembly can also selectively be changed while the printhead is parked.Note that this structure is not required for all embodiments; otheralternatives are also possible, such in which only the printheadassembly moves (or one of the printheads is moved) and the measurementassembly is stationary or in which no parking of the printhead assemblyis necessary.

Generally speaking, the optics used for droplet measurement will includea light source 717, an optional set of light delivery optics 719 (whichdirect light from the light source 717 to the measurement area 715 asnecessary), one or more light sensors 721, and a set of recovery optics723 that direct light used to measure the droplet(s) from themeasurement area 715 to the one or more light sensors 721. The motionsystem 711A optionally moves any one or more of these elements togetherwith the chassis 709 (e.g., together with the imaging area) in a mannerthat permits the direction of post-droplet measurement light from themeasurement area 715 to a below-plane location. In one embodiment, thelight delivery optics 719 and/or the light recovery optics 723 usemirrors that direct light to/from measurement area 715 along a verticaldimension parallel to droplet travel, with the motion system moving eachof elements 709, 717, 719, 721 and 723 as an integral system duringdroplet measurement; this setup presents an advantage that focus neednot be recalibrated relative to measurement area 715. As noted bynumeral 711C, the light delivery optics are also used to optionallysupply source light from a location below the dimensional plane 713 ofthe measurement area, e.g., with both light source 717 and lightsensor(s) 721 directing/collecting light from beneath the measurementarea, as generally illustrated. As noted by numerals 725 and 727, theoptics system can optionally include lenses for purposes of focus, aswell as photodetectors (e.g., for non-imaging techniques that do notrely on processing of a many-pixeled “picture”). Note once again thatthe optional use of z-motion control over the chassis permits optionalengagement and disengagement of the optics system, and precisepositioning of measurement area 715 proximate to any group of nozzles,at any point in time while the printhead assembly is “parked.” Suchparking of the printhead assembly 703 and xyz-motion of the opticssystem 701 is not required for all embodiments. Other combinations andpermutations are also possible.

FIG. 7B provides flow of a process associated with droplet measurementfor some embodiments. This process flow is generally designated usingnumeral 731 in FIG. 7B. More specifically, as indicated by referencenumeral 733, in this particular process, the printhead assembly is firstparked, for example, in a service station (not shown) of a printer ordeposition apparatus. A droplet measurement device is then engaged (735)with the printhead assembly, for example, by selective engagement ofpart or all of a droplet measurement system through movement from belowa deposition plane into a position where an optics system of the dropletmeasurement system is capable of measuring droplets from many nozzlesconcurrently. Per numeral 737, this motion relative of one or moreoptics-system components relative to a parked printhead can optionallybe performed in x, y and z dimensions.

As indicated in the aforementioned patent applications which have beenincorporated by reference, even a single nozzle and associated nozzlefiring drive waveform (i.e., pulse(s) or signal level(s) used to jet adroplet) can produce droplet volume, trajectory, and velocity thatvaries slightly from droplet-to-droplet. In accordance with teachingsherein, in one embodiment, the droplet measurement system, as indicatedby numeral 739, optionally obtains n measurements per droplet of adesired parameter, to derive statistical confidence regarding theexpected properties of that parameter. In one implementation, themeasured parameter can be volume, whereas for other implementations, themeasured parameter can be flight velocity, flight trajectory, nozzleposition error (e.g., nozzle bow) or another parameter, or a combinationof multiple such parameters. In one implementation, “n” can vary foreach nozzle, whereas in another implementation, “n” can be a fixednumber of measurements (e.g., “24”) to be performed for each nozzle; instill another implementation, “n” refers to a minimum number ofmeasurements, such that additional measurements can be performed todynamically adjust measured statistical properties of the parameter orto refine confidence. Clearly, many variations are possible. Inconnection with the system described earlier, a measurement populationcan be built up immediately (i.e., by taking multiple dropletmeasurements for a given nozzle array during a single measurementiteration, that is, without moving the droplet measurement system to adifferent nozzle set), or by taking a single measurement and building upa measurement population through later measurements (e.g., asmeasurement continually precesses through a circular range of nozzlesover time).

For the example provided by FIG. 7B, it should be assumed that dropletvolume is being measured, so as to obtain an accurate mean representingexpected droplet volume from a given nozzle and a tight confidenceinterval. This enables optional planning of droplet combinations (usingmultiple nozzles and/or drive waveforms) while reliably maintainingdistributions of composite ink fills in a target region about anexpected target (i.e., relative to a composite of droplet means). Asnoted by optional process boxes 741 and 743, contemplated opticalmeasurement processes ideally enable instantaneous or near instantaneousmeasurement and calculation of volume (or other desired parameter) ofmany nozzles at once, for example, using a clear film and belowdeposition plane capture (i.e., from an opposite side of the film tothat used for deposition); with such fast-measurement, it becomespossible to frequently and dynamically update volume measurements, forexample, to account for changes over time in ink properties (includingviscosity and constituent materials), temperature, nozzle clogging orage and other factors. Building on this point, for example, with a10,000 nozzle printhead assembly, it is expected that large measurementpopulations for each of the thousands of nozzles can be obtained inminutes, rendering it feasible to frequently and dynamically performdroplet measurement. As noted earlier, in one optional embodiment,droplet measurement (or measurement of other parameters, such astrajectory and/or velocity) can be performed as a periodic, intermittentprocess, with the droplet measurement system being engaged according toa schedule, or in between substrates (e.g., as substrates are beingloaded or unloaded), or stacked against other assembly and/or otherprinthead maintenance processes, to effectively collect many data points(and thereby build a statistical distribution representing each nozzle)over many measurement intervals. Note that for embodiments that permitalternate nozzle drive waveforms to be used in a manner specific to eachnozzle, such a rapid measurement system facilitates planned scan pathadjustment, nozzle qualification/disqualifications, and planned dropletcombinations of droplets produced by various nozzle-waveform pairings,as alluded to earlier and in the aforementioned patent applicationswhich have been incorporated by reference. Per numerals 745 and 747, bymeasuring expected droplet volume to a precision of better than 0.01 pL,it becomes possible to plan for very precise droplet usage, where use ofdroplets can also be planned (ideally) to 0.01 pL resolution, and wheremeasurement error in one embodiment is effectively reduced so as toprovide for 3σ confidence (or other statistical measure, such as 4σ, 5σ,6σ, etc.) relative to allowable droplet volume. The same is true fordroplet position and/or velocity and/or nozzle bow. For example, bymeasuring expected position to a precision of better than one micron (oranother distance measure), it becomes possible to provide for veryprecise depositions; expected position can be measured to a range of aspecific Cartesian point and standard deviation (or, e.g., 4σ, 5σ, 6σspread) around such a point). Once sufficient measurements are taken forvarious droplets, fills involving combinations of those droplets can beevaluated and used to plan printing (748) in the most efficient mannerpossible. As indicated by separation line 749, droplet measurement canbe performed with intermittent switching back and forth between active“on-line” printing processes and “off-line” measurement and calibrationprocesses; note that to minimize manufacturing system downtime, suchmeasurement is typically performed while the printer is tasked withother processes, e.g., during substrate loading and unloading. Pernumeral 751, in one embodiment, the clear film or tape can be speciallyselected (or treated) so as to optimize capture of droplet propertiesfor the particular ink under analysis (i.e., given chemical or fluidicproperties of that ink), for purposes of facilitating image captureand/or analysis. For example, the ink in some applications is a monomerthat will later be cured by an ultraviolet light cure process to becomea polymer; to facilitate capture of droplet properties, the clear filmcan be selected so as to have physical, color, absorbance, fixing,curing, or other properties to as to enhance the prevision with whichsuch a material can be analyzed by the image capture system. Finally,per numeral 753, either the film (tape) or the droplet measurementsystem as a whole (or both) can be designed for modular replacement, soas to minimize measurement system and printing system downtime.

During printing, nozzle (and nozzle-waveform) measurement can beperformed on a rolling basis, precessing through a range of nozzles witheach break in between substrate print operations. Whether engaged tomeasure all nozzles anew, or on such a rolling basis, the same basicprocess of FIG. 7B can be employed for measurement. To this effect, whenthe droplet measurement device is engaged for a new measurement (eitheron the heels of prior measurement or on the heels of a substrate printoperation), the system software loads a pointer which identifies thenext nozzle set for which measurements are to be taken (e.g., for asecond printhead, “nozzle window having an upper left corner at nozzle2,312”). In the case of initial measurement (e.g., responsive toinstallation of a new printhead, or a recent boot-up, or a periodicprocess such as a daily measurement process), the pointer would point toa first nozzle for a printhead, e.g., “nozzle 2, 001.” This nozzleeither is associated with a specific imaging grid access or one islooked-up from memory. The system uses the provided address to advancethe droplet measurement system (e.g., the measurement area referencedearlier) to a position corresponding to the expected nozzle position.Note that in a typical system, the mechanical throws associated withthis movement are quite precise, i.e., to approximately micronresolution. The system optionally at this time searches for nozzleposition about the expected micron-resolution position, and finds thenozzle and centers on its position based on image analysis of theprinthead within a small micron-distance from the estimated gridposition. For example, a zig-zag, spiral or other search pattern can beused to search about the expected position for a nozzle or fiducialbearing a predetermined positional relationship relative to the desiredset. A typical pitch distance between nozzles might be on the order of250 microns, whereas nozzle diameter might be on the order of 10-20microns.

FIG. 7C provides a flow diagram relating to nozzle qualification. In oneembodiment, droplet measurement is performed to yield statistical models(e.g., distribution and mean) for each nozzle and for each waveformapplied to any given nozzle, for any of and/or each of droplet volume,velocity and trajectory. Thus, for example, if there are two choices ofwaveforms for each of a dozen nozzles, there are up to 24waveform-nozzle combinations or pairings; in one embodiment,measurements for each parameter (e.g. volume) are taken for each nozzleor waveform-nozzle pairing sufficient to develop a robust statisticalmodel. Note that despite planning, it is conceptually possible that agiven nozzle or nozzle-waveform pairing may yield an exceptionally widedistribution, or a mean which is sufficiently aberrant that it should bespecially treated. Such special treatment applied in one embodiment isrepresented conceptually by FIG. 7C.

More particularly, a general method is denoted using reference numeral781. Data generated by the droplet measurement device is stored inmemory 785 for later use. During the application of method 781, thisdata is recalled from memory and data for each nozzle or nozzle-waveformpairing is extracted and individually processed (783). In oneembodiment, a normal random distribution is built for each variable tobe qualified, as described by a mean, standard deviation and number ofdroplets measured (n), or using equivalent measures. Note that otherdistribution formats (e.g., Student's-T, Poisson, etc.), can be used.Measured parameters are compared to one or more ranges (787) todetermine whether the pertinent droplet can be used in practice. In oneembodiment, at least one range is applied to disqualify droplets fromuse (e.g., if the droplet has a sufficiently large or small volumerelative to desired target, then that nozzle or nozzle-waveform pairingcan be excluded from short-term use). To provide an example, if 10.00 pLdroplets are desired, then a nozzle or nozzle-waveform linked to adroplet mean more than, e.g., 1.5% away from this target (e.g., <9.85 pLor >10.15 pL) can be excluded from use. Range, standard deviation,variance, or another spread measure can also or instead be used. Forexample, if it is desired to have droplet statistical models with anarrow distribution (e.g., 3σ<1.005% of mean), then droplets withmeasurements not meeting this criteria can be excluded. It is alsopossible to use a sophisticated/complex set of criteria which considersmultiple factors. For example, an aberrant mean combined with a verynarrow spread might be okay, e.g., if spread (e.g., 3σ) away frommeasured (e.g., aberrant) mean μ is within 1.005%, then an associateddroplet can be used. For example, if it is desired to use droplets with3σ volume within 10.00 pL±0.1 pL, then a nozzle-waveform pairingproducing a 9.96 pL mean with ±0.8 pL 3σ value might be excluded, but anozzle-waveform pairing producing a 9.93 pL mean with ±0.3 pL 3σ valuemight be acceptable. Clearly many possibilities are possible accordingto any desired rejection/aberration criteria (789). Note that this sametype of processing can be applied for per-droplet flight angle andvelocity, i.e., it is expected that flight angle and velocity pernozzle-waveform pairing will exhibit statistical distribution and,depending on measurements and statistical models derived from thedroplet measurement device, some droplets can be excluded. For example,a droplet having a mean velocity or flight trajectory that is outside of5% of normal, or a variance in velocity outside of a specific targetcould hypothetically be excluded from use. Different ranges and/orevaluation criteria can be applied to each droplet parameter measuredand provided by storage 785.

Note that depending on the rejection/aberration criteria 789, droplets(and nozzle-waveform combinations) can be processed and/or treated indifferent manners. For example, a particular droplet not meeting adesired norm can be rejected (791), as mentioned. Alternatively, it ispossible to selectively perform additional measurements for the nextmeasurement iteration of the particular nozzle-waveform pairing; as anexample, if a statistical distribution is too wide, it is possible tospecially perform additional measurements for the particularnozzle-waveform pairing so as to improve tightness of a statisticaldistribution through additional measurement (e.g., variance and standarddeviation are dependent on the number of measured data points). Pernumeral 793, it is also possible to adjust a nozzle drive waveform, forexample, to use a higher or lower voltage level (e.g., to providegreater or lesser velocity or more consistent flight angle), or toreshape a waveform so as to produce an adjusted nozzle-waveform pairingthat meets specified norms. Per numeral 794, timing of the waveform canalso be adjusted (e.g., to compensate for aberrant mean velocityassociated with a particular nozzle-waveform pairing). As an example(alluded to earlier), a slow droplet can be fired at an earlier timerelative to other nozzles, and a fast droplet can be fired later in timeto compensate for faster flight time. Many such alternatives arepossible. Finally, per numeral 795, any adjusted parameters (e.g.,firing time, waveform voltage level or shape) can be stored andoptionally, if desired, the adjusted parameters can be applied toremeasure one or more associated droplets. After each nozzle-waveformpairing (modified or otherwise) is qualified (passed or rejected), themethod then proceeds to the next nozzle-waveform pairing, per numeral797.

The schemes represented above can also be used to measure nozzle bow(and of course, to qualify or disqualify nozzles on this basis). Thatis, as an example, if it is assumed that a grouping of depositeddroplets original from a single, common exact nozzle position, but areclustered off-center in the direction orthogonal to printhead substratescanning motion, the nozzle in question could be offset relative toother nozzles in the same row or column. Such aberration can lead toidealized droplet firing deviations that can be taken into account inplanning precise combinations of droplets, i.e., any such “bow” orindividual nozzle offset is stored and used to qualify/disqualifynozzles or as part of print scan planning, as discussed earlier, withthe printing system using the differences of each individual nozzle in aplanned manner rather than averaging out those differences. In anoptional variation, the same technique can be used to determinenon-regular nozzle spacing along the printhead scanning direction (i.e.,the fast print axis), although for the depicted embodiment, any sucherror is subsumed in correction for droplet velocity deviations (e.g.,any such spacing error can be corrected for by adjustments to nozzlevelocity, for example, effectuated by minor changes to a drive waveformused for the particular nozzle). To determine cross-scan-axis bow of anozzle producing a cluster of droplets, the respective trajectories areeffectively reverse plotted (or otherwise mathematically applied) withother measurement trajectories for the same nozzle and used to identifya mean cross-scan-axis position of the specific nozzle under scrutiny.This position may be offset from an expected location for such a nozzle,which could be evidence of nozzle bow.

As stated before and as implied by this discussion, one embodimentbuilds a statistical distribution for each nozzle for each parameterbeing measured, for example, for volume, velocity, trajectory, nozzlebow, and potentially other parameters. As part of these statisticalprocesses, individual measurements can be thrown out or used to identifyerrors. To cite a few examples, if a droplet measurement is obtainedhaving a value that is so far removed from other measurements of thesame nozzle that the measurement could represent a firing or measurementerror; in one implementation, the system discards this measurement ifdeviant to a point that exceeds a statistical error parameter. If nodroplet is seen at all, this could be evidence that the dropletmeasurement system is at the wrong nozzle (wrong position), or has afiring waveform error or that a nozzle under scrutiny is inoperative. Anerror handling process can be employed to make appropriate adjustmentsincluding taking any new or additional measurements as necessary.

Note that, although not separately called out by FIGS. 7A-C, thedepicted measurement process would typically be performed for eachalternate waveform available for use with each nozzle. For example, ifeach nozzle had four different piezoelectric drive waveforms that couldbe selected, the measurement process might generally be repeated 4 timesfor each group of nozzles; if a particular implementation called for thebuilding of a statistical distribution based on 24 droplets for eachwaveform, then there might be 96 such measurements for one nozzle (24for each of four waveforms, with each measurement being used to developstatistical mean and spread measures for each of droplet velocity,trajectory and volume, and for estimated nozzle position (e.g., forpurposes of assessing nozzle bow). In one contemplated embodiment, anynumber of waveforms can be shaped or otherwise generated, and the systemmeasures droplet parameters associated with one or more preselectedwaveforms and then stores these parameters for later use in printingand/or print planning. These parameters can also be used in determiningwhether to keep (and store) the waveform for use in printing (e.g., aspart of a pre-selected set of permissible waveforms), or to select adifferent waveform and measure parameters for that waveform.

Through the use of precision mechanical systems and droplet measurementtechniques, the disclosed methodology permits very high accuracymeasurement of individual nozzle characteristics, including mean dropletmetrics for each of the mentioned parameters (e.g., volume, velocity,trajectory, nozzle position, and other parameters). As should beappreciated, the mentioned techniques facilitate a high degree ofuniformity in manufacturing processes, especially OLED devicemanufacture processes, and therefore enhance reliability. By providingfor control efficiencies, particularly as to speed of dropletmeasurement and the stacking of such measurement against other systemprocesses in a manner calculated to reduce overall system downtime, theteachings presented above help provide for a faster, less expensivemanufacturing process designed to provide both flexibility and precisionin the fabrication process.

FIG. 8A shows a cross-sectional view of a typical layout within anindustrial fabrication apparatus (e.g., associated with a printer insuch an apparatus) 801. More specifically, printing is seen to beperformed within a print enclosure chamber 803, such that an ambientatmosphere can be controlled (“controlled atmosphere”); such control istypically performed to exclude unwanted particulate, or otherwise toperform printing in the presence of a specific gas constituency (forexample, nitrogen, a noble gas, etc.). Generally speaking, a substrate813 is generally introduced into the printer using an atmospheric bufferchamber (not shown) and conveyed to a flotation support table 815 usinga mechanical handler, which also aligns the substrate properly forprinting via detection of one or more fiducials on the substrate (thesefiducials and a camera or other optical detector used to detect precisesubstrate position are not shown in FIG. 8A). Printing is performedusing a printhead assembly 807 which is moved back and forth (asdepicted by arrows 809) along a traveler 811 in the direction of a “slowprint axis.” The printhead assembly 807 is depicted as a single objectbut may be a complex assembly that mounts multiple printheads (e.g., 6,10 or another number), each one having hundreds to thousands of printnozzles (e.g., two thousand nozzles each). The printhead assembly 807deposits a liquid ink onto the substrate 813 at precise position pointsto precise thicknesses, where the ink includes a material that will forma permanent layer of one or more products to be fabricated on thesubstrate 813. For example, such a material can be an organic orinorganic material, a conductor or insulator, a plastic, a metal, orsome other type of material. In a typical application, the substrate 813is more than one meter wide and several meters long and is used tosimultaneously fabricate multiple OLED displays arrayed on thesubstrate; each layer is deposited as part of an integral print processacross all such “subpanels” (i.e., across multiple such displaysin-fabrication) with the individual displays eventually being cut fromthe substrate via another process. Each print process can deposit adifferent ink to a specified thickness, for example, conductors,insulators, light generating elements, semiconductor materials,encapsulation and so forth, using print instructions specific to theparticular layer. In an assembly line process, there can be multipleprinters arranged at different positions or used in successive,different deposition processes. For OLED materials, an ink is depositedfor a particular layer, and following deposition, the substrate isremoved from the chamber and advanced to a cure chamber (not shown)where the deposited ink can be cured, dried, heated or otherwiseprocessed to impart permanency to deposited material. Note that thedepicted arrangement represents a “split-axis” printer, i.e., thefloatation table 815 and associated handlers (not shown) advance thesubstrate into and out of the drawing page, along the direction of a Yaxis 825 seen at a dimensional reference 823 near the bottom right ofthe FIG.

To perform droplet measurement, the printhead assembly 807 isselectively advanced outside of a normal print area to a point where itmay be parked in a service station, generally associated with a secondenclosure environment 805. This second environment is optional, but isadvantageous to permit inspection, printhead substitution and othermaintenance forms without having to vent the print enclosure chamber803. To park the printhead assembly 807, the assembly is moved to alocation generally seen at the left side of the FIG., and is thenadvanced vertically in order to seal the printhead assembly 807 againsta chamber for the second enclosure environment, as represented by dashedline position 819. In this “parked” position, the droplet measurementsystem 817 can be controlled (e.g., in three dimensions) to selectivelytransport a measurement area to mimic a substrate deposition height inproximity to any desired nozzle area.

Note that as referenced above, in a typical application, it is desiredto keep the fabrication apparatus 801 “online” and in-use as much aspossible. To this effect, rather than performing droplet measurement ata time when the apparatus 801 could be used for printing (and forproduct manufacture), in one embodiment, measurement and printing are“ping-ponged,” i.e., each time a substrate (e.g., 813) is loaded orunloaded, during a time interval between print operations, the printheadassembly 807 is advanced to the service station and is partiallycalibrated (e.g., as to a rolling subset of print nozzles and/or printnozzle waveforms) in order to build a robust set of measurements foreach nozzle, updated to be current, and maintained in a manner todevelop statistical measurement populations, as described previously.Note that any one of these features may be considered optional, and isnot essential for practice of the disclosed techniques.

FIG. 8B provides a plan view of the substrate and printer as they mightappear during the deposition process, taken along lines B-B from FIG.8A. The print enclosure chamber is once again generally designated byreference numeral 803, while the second enclosure environment used fordroplet measurement is generally designated by reference numeral 805.Within the print enclosure chamber, the substrate to be printed upon isonce again generally designated by numeral 813, and the support tableused to transport the substrate is generally designated by numeral 815.Generally speaking, any xy coordinate of the substrate is reached by acombination of movements, including x- and y-dimensional movement of thesubstrate by the support table (e.g., using flotation support, asdenoted by numeral 857) and using “slow axis” x-dimensional movement ofone or more printheads 807 along a traveler 811, as generallyrepresented by arrows 809. As mentioned, the flotation table andsubstrate handling infrastructure are used to move the substrate duringprinting along one or more “fast axes,” as necessary. The printhead isseen to have plural nozzles 865, each of which is separately controlledby a firing pattern derived from a print image (e.g., to effectuateprinting of columns corresponding to printer grid points as theprinthead is moved from left-to-right and vice-versa along the “slowaxis”); note that while only a few print nozzles are graphicallydepicted in the FIG., in practice, there are hundreds to many thousandsof such nozzles, arranged in many columns and rows. With relative motionbetween the one or more printheads and the substrate provided in thedirection of the fast axis (i.e., the y-axis), printing describes aswath that typically follows individual rows of printer grid points. Theprinthead assembly can also optionally be rotated or otherwise adjustedto vary effective nozzle spacing, per numeral 867. Note that multiplesuch printheads can be used together, oriented with x-dimension,y-dimension, and/or z-dimensional offset relative to one another asdesired (see axis legend 823 in FIG. 8B). The printing operationcontinues until the entire target region (and any border region) hasbeen printed with ink, as desired, with relative printheadassembly/substrate motion represented by the vertical element ofdepicted transport directions 857. Following deposition of the necessaryamount of ink, the substrate is finished, such as via use of anultraviolet (UV) or other cure or hardening process that forms apermanent layer from the liquid ink. As noted earlier, as substrates areloaded or unloaded for printing, the printhead is advanced to amaintenance station and is sealed to a second enclosure environment 805.In practice, this second enclosure environment as noted is made a subsetof the print enclosure chamber 803, such that a printhead can be changedwithout having to vent the print enclosure chamber as a whole. Withinthe second enclosure environment 805, the droplet measurement system 817(seen in dashed lines to lie below traveler 811) is selectively engaged(again, advantageously using three dimensional articulation of thedroplet measurement system as a whole, e.g., of a chassis thereof), formeasurement as referenced earlier.

FIG. 9 provides a chart that illustrates measured droplet positionsrelative to positions expected for those droplets for each of manynozzles. More specifically, the chart is generally designated by numeral901 and shows a group of approximately 40 nozzles. It should be assumedthat the chart 901 represents image data, for example, processed aboveas described with reference to FIGS. 6A-C in order to obtain a measureddroplet position (i.e., such as position 903) relative to acorresponding expected position (i.e., such as position 904). Severalfeatures should be noted relative to FIG. 9. First, the nozzles are seento be arranged in rows of nozzles that are slightly staggered inposition, as represented by graphic 905; this feature permits veryprecise spacing of droplets, e.g., while manufacturing tolerances aresuch that nozzles are positioned in a cross-scan direction severalhundred microns apart, slight staggering from row to row permitsalternate nozzle usage (for example, the nozzle corresponding toposition 906 relative to the nozzle corresponding to position 907, whichpermits very tight placement of droplets, e.g., to within 20 microns orless of any desired position on a substrate. Second, the chart 901indirectly emphasizes benefits provided by positional calibration of thedroplet measurement system relative to a printhead, e.g., it isimportant that the system know exactly which nozzle corresponds toposition 903 and expected position 904, so as to be able to match anymeasured data (and any nozzle qualification or adjustment) with thecorrect nozzle. Through image processing, precise positional offsets canbe determined for each nozzle, and factored into nozzle qualificationand print planning. Finally, note again that the use of a clear filmpotentially permits image capture not only of deposited droplets, but ofthe nozzle as well (e.g., captured through the clear film), facilitatingperformance of distance analysis by software. This is not required forall embodiments, e.g., through an understanding of how the capturedimage of the film corresponds to nozzle plate position, the software caneasily also infer nozzle position relative to the captured image, and onthis basis compute positional offsets. In the context of FIG. 9, thenumeral 904 in one embodiment represents image nozzle position with anydeviation between measured position 903 and position 904 representingdroplet velocity and/or bow. Also, while FIG. 9 represents positionaloffset of droplets relative to expected droplet position, similaranalysis can also be used to measure droplet volume, for example, bycomparing droplet color (e.g., grayscale value), droplet diameter, orother features of the captured image to a standard, and computingdroplet volume therefrom. Through the use of repeated, additionalmeasurements for each nozzle or nozzle-waveform pairing, the system canreadily build distributions for any desired droplet parameter on aper-nozzle or per-nozzle waveform basis.

FIG. 10 shows a flow diagram 1001 associated with determining dropletvolumes from a captured image. Per numeral 1003, a captured imagerepresenting droplets produced by an array of nozzles is first retrievedfrom memory. This image is then filtered as appropriate to segment justthe droplets of interest (e.g., with varying color intensity accordingto thickness or ink concentration on the deposited medium), per numeral1005. Note that such the filtered image can be a first, second, third orother instance of filtration performed to measure a specific parameterfrom a single image (e.g., other instances can be used to computeddistances, positions, offset, and so forth for droplet velocity,position, nozzle position and so forth). Per numeral 1007, any color hueis then processed to correlate that hue with ink thickness or density;for example, if deposited ink has a slightly reddish tint, then a“redder” portion of the image would typically represent greaterthickness. Note that for embodiments where multiple droplets aredeposited from each nozzle at-once, there can be multiple visibledroplets that overlap, and thickness processing 1007 preferably takesthis into account, segmenting any individual droplet; this is notrequired for all embodiments, e.g., if it is known that five dropletsfor example have been deposited, it might suffice to compute overallvolume and to divide by five. Per numeral 1009, droplet radii are thencalculated as referenced earlier (or aggregate ink coverage) and used inconnection with the derived thickness measure to compute total depositedink. Importantly, the clear film used as a deposition surface ideallyfixes deposited ink and therefore may differ from an actual depositionsurface used in active printing (e.g., a glass substrate); as depictedby numeral 1008 therefore, a stored standard specific to the depositionmaterial is retrieved and used in connection with thickness processing,volume calculation 1011 or both to derive correct droplet volumeestimates. Finally, measurement data is stored per numeral 1013 and anycomputed per-nozzle or per-nozzle-waveform distributions (e.g., mean andspread) are updated for use in print or scan planning. Note thatanalogous comparisons to a standard and raw value (or offset)computation can be applied for many other parameters other than volume,as suitable to the particular application.

Reflecting on the various techniques and considerations introducedabove, a manufacturing process can be performed to mass produce productsquickly and at low per-system cost. By providing for fast, repeatableprinting techniques, it is believed that printing can be substantiallyimproved, for example, reducing per-layer printing time to a smallfraction of the time that would be required without the techniquesabove. Again returning to the example of large HD television displays,it is believed that each color component layer can be accurately andreliably printed for large substrates (e.g., generation 8.5 substrates,which are approximately 220 cm×250 cm) in one hundred and eighty secondsor less, or even ninety seconds or less, representing substantialprocess improvement. Improving the efficiency and quality of printingpaves the way for significant reductions in cost of producing large HDtelevision displays, and thus lower end-consumer cost. As noted earlier,while display manufacture (and OLED manufacture in particular) is oneapplication of the techniques introduced herein, these techniques can beapplied to a wide variety of processes, computer, printers, software,manufacturing equipment and end-devices, and are not limited to displaypanels.

The foregoing description and in the accompanying drawings, specificterminology and drawing symbols have been set forth to provide athorough understanding of the disclosed embodiments. In some instances,the terminology and symbols may imply specific details that are notrequired to practice those embodiments. The terms “exemplary” and“embodiment” are used to express an example, not a preference orrequirement.

As indicated, various modifications and changes may be made to theembodiments presented herein without departing from the broader spiritand scope of the disclosure. For example, features or aspects of any ofthe embodiments may be applied, at least where practical, in combinationwith any other of the embodiments or in place of counterpart features oraspects thereof. Thus, for example, not all features are shown in eachand every drawing and, for example, a feature or technique shown inaccordance with the embodiment of one drawing should be assumed to beoptionally employable as an element of, or in combination of, featuresof any other drawing or embodiment, even if not specifically called outin the specification. Accordingly, the specification and drawings are tobe regarded in an illustrative rather than a restrictive sense.

1. (canceled)
 2. A method of fabricating a thin-film layer of anelectronic product, the method comprising: receiving a substrate into amanufacturing system; while the substrate is in a printing area of themanufacturing system, printing droplets of a liquid onto the substratefrom respective nozzles of one or more printheads of the manufacturingsystem, the droplets of the liquid to coalesce to form a liquid coat onthe substrate, the liquid carrying a film-forming material, whereinthere are at least five hundred of the respective nozzles carried by theone or more printheads; processing the liquid coat to solidify thefilm-forming material so as to form the thin-film layer therefrom; andunloading the substrate from the manufacturing system; wherein themethod further comprises calibrating droplets produced by respectiveones of the at least five hundred nozzles, in situ within themanufacturing system, for at least one of droplet volume, droplet size,droplet shape or droplet landing location, by robotically transportingthe one or more printheads to a location within the manufacturingsystem, outside of the printing area, while the one or more printheadsare at the location, using a droplet measurement system to collectivelyimage droplets respectively produced by nozzles in a subset of the atleast five hundred respective nozzles and, based on the collective imageof the droplets produced by the nozzles in the subset, to calculate theat least one value of droplet volume, droplet shape, droplet size ordroplet landing location for droplets produced by each of the nozzles inthe subset, and repeating the using of the droplet measurement system tocollectively image droplets and to calculate the at least one value in amanner so as to compute the at least one value for each one of the atleast five hundred of the respective nozzles carried by the one or moreprintheads, and robotically transporting the one or more printheads fromthe location to the printing area for the printing, wherein themanufacturing system performs the printing in a manner dependent on themeasurements of the at least one of droplet volume, droplet shape,droplet size or droplet landing location for the at least five hundrednozzles.
 3. The method of claim 2, wherein the droplet measurementdevice is to provide a translucent test substrate having a first side,onto which the droplets produced by the subset are deposited atrespective positions on the first side, and wherein the translucent testsubstrate has a second side, through which the collective image of thedroplets is captured by the image capture system.
 4. The method of claim3, wherein the droplet measurement system comprises a chassis thatmounts a reel of tape, the tape providing the translucent testsubstrate, and that mounts a camera and a tape advancement system,wherein the chassis defines a window and wherein tape advancement systemis to advance the tape relative to the window such that a first side ofthe tape is to receive the droplets respectively produced by the nozzlesin the subset, and such that the camera is to image the dropletsdeposited onto the first side of the tape through the window and througha second side of the tape, and wherein the method further comprisesrobotically transporting the droplet measurement system while the one ormore printheads are at the location, without moving the one or moreprintheads, and advancing the tape relative to the window so as toperform the repeating.
 5. The method of claim 3, wherein the at leastone value is one of droplet size or droplet volume, for each nozzle ofthe at least five hundred nozzles, and wherein the image processingsystem is to compute the one of droplet size or droplet volume byidentifying an area each droplet in the image occupies on the first sideof the tape, and by computing the at least one value for a correspondingnozzle in the subset in dependence on the identified area.
 6. The methodof claim 2, wherein the manufacturing system performs the printing inthe manner dependent on the measurements by selectively assigningnozzles to print respective ones of the droplets of the liquid onto thesubstrate in dependence on the measurements.
 7. The method of claim 2,wherein the manufacturing system performs the printing in the mannerdependent on the measurements by selectively disqualifying nozzles fromuse in the printing of the droplets of the liquid onto the substrate independence on the measurements.
 8. The method of claim 2, wherein thedroplet measurement system comprises a transport system adapted to movean image capture device of the droplet measurement system in at leasttwo dimensions while the one or more printheads are stationary at thelocation, so as to robotically reposition the image capture device toimage droplets produced by different subsets of the nozzles withoutrequiring relative movement between the one or more printheads and themanufacturing system.
 9. The method of claim 2, wherein themanufacturing system comprises a gas enclosure to hold a controlledatmosphere, and wherein the printing of the droplets of the liquid ontothe substrate and the calibrating of the droplets using the dropletmeasurement system are each performed within the gas enclosure andwithin the controlled atmosphere.
 10. The method of claim 2, wherein themanufacturing system comprises at least one of a curing system or abaking system, and wherein the processing of the liquid coat comprisescuring or baking the liquid coat, using the at least one of the curingsystem or the baking system, to solidify the film-forming materialrelative to the liquid.
 11. The method of claim 10, wherein theprocessing of the liquid coat comprises transporting the substrate fromthe printing area to a processing area at which the curing or baking isperformed, and wherein the repeating is performed, at least in part,when the substrate is at the processing area.
 12. The method of claim10, wherein the electronic product comprises a light-emitting device,and wherein the thin-film layer comprises a light generating layer ofthe light-emitting device.
 13. A method of fabricating a thin-film layerof electronic products, the method comprising: for each substrate in aseries of substrates, receiving the substrate into a manufacturingsystem, while the substrate is in a printing area of the manufacturingsystem, printing droplets of a liquid onto the substrate from respectivenozzles of one or more printheads of the manufacturing system, thedroplets of the liquid to coalesce to form a liquid coat on thesubstrate, the liquid carrying a film-forming material, wherein thereare at least five hundred of the respective nozzles carried by the oneor more printheads, processing the liquid coat to solidify thefilm-forming material so as to form the thin-film layer therefrom, andunloading the substrate from the manufacturing system; wherein themethod further comprises, calibrating droplets produced by respectiveones of the at least five hundred nozzles, in situ within themanufacturing system, for at least one of droplet volume, droplet size,droplet shape or droplet landing location, by robotically transportingthe one or more printheads to a location within the manufacturingsystem, outside of the printing area, in between printing on respectiveones of the substrates in the series, while the one or more printheadsare at the location, using a droplet measurement system to collectivelyimage droplets respectively produced by nozzles in a subset of the atleast five hundred respective nozzles and, based on the collective imageof the droplets produced by the nozzles in the subset, to calculate theat least one value of droplet volume, droplet shape, droplet size ordroplet landing location for droplets produced by each of the nozzles inthe subset, and robotically transporting the one or more printheads fromthe location to the printing area for the printing; wherein the methodfurther comprises repeating the using of the droplet measurement systemto collectively image droplets and calculate the at least one value in amanner so as to calculate the at least one value for each one of the atleast five hundred of the respective nozzles carried by the one or moreprintheads, and wherein for different successive pairs of the substratesin the series, the nozzles in the subset are changed, in a manner suchthat the droplet measurement system incrementally measures the at leastone of droplet volume, droplet shape, droplet size or droplet landinglocation for each one of the at least five hundred nozzles in betweenprinting of the droplets onto pairs of the substrates in the series; andwherein, for each of the substrates, the manufacturing system performsthe printing in a manner dependent on the measurements of the at leastone of droplet volume, droplet shape, droplet size or droplet landinglocation for the at least five hundred nozzles.
 14. The method of claim13, wherein the droplet measurement device is to provide a translucenttest substrate having a first side, onto which the droplets produced bythe subset are deposited at respective positions on the first side, andwherein the translucent test substrate has a second side, through whichthe collective image of the droplets is captured by the image capturesystem.
 15. The method of claim 14, wherein the droplet measurementsystem comprises a chassis that mounts a reel of tape, the tapeproviding the translucent test substrate, that mounts a camera and atape advancement system, wherein the chassis defines a window andwherein tape advancement system is to advance the tape relative to thewindow such that a first side of the tape is to receive the dropletsrespectively produced by the nozzles in the subset, and such that thecamera is to image the droplets deposited onto the first side of thetape through the window and through a second side of the tape, andwherein the method further comprises robotically transporting thedroplet measurement system while the one or more printheads are at thelocation, without moving the one or more printheads, and advancing thetape relative to the window so as to perform the repeating.
 16. Themethod of claim 15, wherein the at least one value is one of dropletsize or droplet volume, for each nozzle of the at least five hundrednozzles, and wherein the image processing system is to compute the oneof droplet size or droplet volume by identifying an area each droplet inthe image occupies on the first side of the tape, and by computing theat least one value for a corresponding nozzle in the subset independence on the identified area.
 17. The method of claim 13, whereinthe manufacturing system performs the printing in the manner dependenton the measurements by selectively assigning nozzles to print respectiveones of the droplets of the liquid onto the substrate in dependence onthe measurements.
 18. The method of claim 13, wherein the manufacturingsystem performs the printing in the manner dependent on the measurementsby selectively disqualifying nozzles from use in the printing of thedroplets of the liquid onto the substrate in dependence on themeasurements.
 19. The method of claim 13, wherein the dropletmeasurement system comprises a transport system adapted to move an imagecapture device of the droplet measurement system in at least twodimensions while the one or more printheads are stationary at thelocation, so as to robotically reposition the image capture device toimage droplets produced by different subsets of the nozzles withoutrequiring relative movement between the one or more printheads and themanufacturing system.
 20. The method of claim 13, wherein themanufacturing system comprises a gas enclosure to hold a controlledatmosphere, and wherein the printing of the droplets of the liquid ontothe substrate and the calibrating of the droplets using the dropletmeasurement system are each performed within the gas enclosure andwithin the controlled atmosphere.
 21. The method of claim 13, whereinthe manufacturing system comprises at least one of a curing system or abaking system, and wherein the processing of the liquid coat comprisescuring or baking the liquid coat, using the at least one of the curingsystem or the baking system, to solidify the film-forming materialrelative to the liquid.
 22. The method of claim 21, wherein theprocessing of the liquid coat comprises transporting the substrate fromthe printing area to a processing area at which the curing or baking isperformed, and wherein the repeating is performed, at least in part,when the substrate is at the processing area.
 23. The method of claim21, wherein the electronic product comprises a light-emitting device,and wherein the thin-film layer comprises a light generating layer ofthe light-emitting device.
 24. The method of claim 13, wherein thethin-film layer is an encapsulation layer that is to encapsulate anelectrically-active component of the electronic product.
 25. A method offabricating a thin-film layer of an electronic product havinglight-emitting elements, the method comprising: receiving a substrateinto a manufacturing system; while the substrate is in a printing areaof the manufacturing system and within a controlled gas environment,printing droplets of a liquid onto the substrate from respective nozzlesof one or more printheads of the manufacturing system, the droplets ofthe liquid to coalesce to form a liquid coat on the substrate, theliquid carrying a film-forming material, wherein there are at least fivehundred of the respective nozzles carried by the one or more printheads;processing the liquid coat to solidify the film-forming material so asto form the thin-film layer therefrom; and unloading the substrate fromthe manufacturing system; wherein the method further comprisescalibrating droplets produced by respective ones of the at least fivehundred nozzles, in situ within the manufacturing system, for at leastone of droplet volume, droplet size, droplet shape or droplet landinglocation, by robotically transporting the one or more printheads to alocation within the manufacturing system, outside of the printing area,while the one or more printheads are at the location, using a dropletmeasurement system to collectively image droplets respectively producedby nozzles in a subset of the at least five hundred respective nozzlesand, based on the collective image of the droplets produced by thenozzles in the subset, to calculate the at least one value of dropletvolume, droplet shape, droplet size or droplet landing location fordroplets produced by each of the nozzles in the subset, and repeatingthe using of the droplet measurement system to collectively imagedroplets and to calculate the at least one value in a manner so as tocompute the at least one value for each one of the at least five hundredof the respective nozzles carried by the one or more printheads, androbotically transporting the one or more printheads from the location tothe printing area for the printing; wherein the manufacturing systemperforms the printing in a manner dependent on the measurements of theat least one of droplet volume, droplet shape, droplet size or dropletlanding location for the at least five hundred nozzles; and wherein thethin-film layer comprises at least one of an encapsulation layer or anelectrically-active layer for each of the light emitting elements.